The present invention relates to a method for producing color prints having high quality and long life which will be available for long periods of conservation.
U.S.A. and Europe, collections of color prints have recently spread, and color prints have been considered as art objects.
In order that color prints are recognized as art objects, the prints should have high quality and long life and should not discolor even during long periods of conservation.
In preparation of color prints, two methods may used: one of them is to use color photographic paper of nagative-positive type, and the other is to use color photographic paper of positive-positive type. As an example of the color photographic paper of positive-positive type, there is Ciba chrome paper, prepared by the silver dye bleach (SDB) process. This type of color photographic paper has great substantiality of color image in comparison with color prints obtained by color development. Therefore, positive-positive type photographic papers prepared by the silver dye bleach process have mainly been used to obtain high quality color prints as art objects. The color prints made under the silver dye bleach process, which was invented by K. Schizel in 1905, remarkably have been improved by successive progress and studies. Papers for such prints and prints made on the papers are now on the market as Ciba chrome paper (hereinafter referred to as "SDB paper" and "SDB print").
The color images of color prints on said SDB paper has outstanding durability in both dark and light discoloration in comparison with other color print materials. Consequently, SDB paper has been considered to be most suitable for color print material which is intended for long periods of conservation. However, in order that a color print is dealt with as an art object, the print should be superlative in its quality in addition to its durability of color.
Prints on the SDB paper now on the market may not necessarily fully satisfy the requirement. It can be said that the quality of color prints is almost always decided by the conscientious color and tone reproductions from the original color film. In this point, the SDB paper has still some defects in the above-said reproductions of color and tone. With respect to the tone characteristic, the tone characteristic becomes too high in contrast. As a result, there is too much contrast between high light portions and shadow portions of a print, and the definition of detail becomes worse. With respect to the color characteristic, there are such defects that light blue (C+M) tends to cyan and also light green (C+Y) tends to strong green of cyan; and further, gray at intermediated density becomes violet and light gray becomes cyan. These defects become obstacles in preparing color prints having high quality.